public class MyLinkedList implements IList{
    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;
        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;
    @Override
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    @Override
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        }else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }

    @Override
    public void addIndex(int index, int data) {
        if(index < 0 || index > size()){
            System.out.println("插入位置不合法");
            return;
        }
        if( index == 0){
            addFirst(data);
            return;
        }
        if( index == size()){
            addLast(data);
            return;
        }
        ListNode cur = head;
        ListNode node = new ListNode(data);
        while(index != 0){
            index--;
            cur = cur.next;
        }
        cur.prev.next = node;
        node.prev = cur.prev;
        node.next = cur;
        cur.prev = node;
    }

    @Override
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val==key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    @Override
    public void remove(int key) {
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }

    }

    @Override
    public void removeAllKey(int key) {
        ListNode cur = head;
        while (cur != null){
            if(cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }

    @Override
    public int size() {
        int len = 0;
        ListNode cur = head;
        while(cur != null){
            len++;
            cur = cur.next;
        }
        return len;
    }

    @Override
    public void clear() {
        ListNode cur = head;
        while(cur != null){
            ListNode curN = cur.next;
            cur.next = null;
            cur.prev = null;
            cur = curN;
        }
        head = null;
        last = null;
    }

    @Override
    public void display() {
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
}
